This invention relates to an ink jet printing process for improving the ozone stability of an inkjet image.
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital signals. There are various methods which may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired image. In one process, known as continuous inkjet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while uniimaged droplets are caught and returned to an ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant which is molecularly dispersed or solvated by a carrier medium. The carrier medium can be a liquid or a solid at room temperature. A commonly used carrier medium is water or a mixture of water and organic co-solvents. Each individual dye molecule is surrounded by molecules of the carrier medium. In dye-based inks, no particles are observable under the microscope. Although there have been many recent advances in the art of dye-based ink jet inks, such inks still suffer from deficiencies such as low optical densities on plain paper and poor light-fastness. When water is used as the carrier medium, such inks also generally suffer from poor water-fastness.
The ink jet receiving elements that can be used with the above mentioned inks must meet several requirements including producing high density images that will not smear, bleed or wander when exposed to water for short periods of time.
U.S. Pat. Nos. 4,632,703, 6,149,722 and 6,015,896, WO 00/08103 and WO 98/49239 relate to inks containing phthalocyanine dyes used in inkjet printing. However, there is no disclosure in these references that these inks would be useful with a recording element containing a porous image-receiving layer.
It is an object of this invention to provide an inkjet printing process for improving the ozone stability of an ink jet image.
These and other objects are achieved in accordance with the present invention which comprises an ink jet printing process for improving the ozone stability of an ink jet image comprising:
a) providing an ink jet recording element comprising a support having thereon a porous image-receiving layer having interconnecting voids; and
b) applying droplets of a liquid ink on the image-receiving layer in an image-wise manner, the ink comprising water, humectant and a metallized, phthalocyanine dye, the metallized, phthalocyanine dye comprising the formula:
MPc(SO3X)a(SO2NRRxe2x80x2)b
wherein:
M represents a metal such as copper, nickel, aluminum, zinc, iron or cobalt;
Pc represents a phthalocyanine nucleus;
X represents hydrogen, alkali metal or an organic cation;
a is from 0to 2;
R represents hydrogen; a substituted or unsubstituted alkyl group having from about 1 to about 15 carbon atoms, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;
Rxe2x80x2 represents a substituted or unsubstituted alkyl group having from about 1 to about 15 carbon atoms containing a hydroxy group, a substituted or unsubstituted aryl group containing a hydroxy group or a substituted or unsubstituted heterocyclic group containing a hydroxy group; and
b is from 1 to 4, with the proviso that a+b is an average of from 3 to 4.
It was found that the ozone stability of an ink jet image was improved using the compounds described herein.
In a preferred embodiment of the invention, the metallized, phthalocyanine dyes which may be used include the following:
MPc(So3X)a(SO2NHRxe2x80x2)b
(M is Cu, and X, Pc, a and b being defined as above)
xe2x80x83MPc(So3X)a(SO2NRRxe2x80x2)b
(R=Rxe2x80x2=xe2x80x94CH2CH2OH, and X, Pc, a and b being defined as above)
In another preferred embodiment of the invention, R represents a substituted or unsubstituted alkyl group having from about 1 to about 15 carbon atoms containing a hydroxy group, an aryl group containing a hydroxy group or a heterocyclic substituent containing a hydroxy group.
The dyes described above may be employed in any amount effective for the intended purpose. In general, good results have been obtained when the dye is present in an amount of from about 0.2 to about 5% by weight of the ink jet ink composition, preferably from about 0.3 to about 3% by weight. Dye mixtures may also be used.
The support for the ink jet recording element used in the invention can be any of those usually used for ink jet receivers, such as paper, resin-coated paper, plastics such as a polyester-type resin such as poly(ethylene terephthalate), polycarbonate resins, polysulfone resins, methacrylic resins, cellophane, acetate plastics, cellulose diacetate, cellulose triacetate, vinyl chloride resins, poly(ethylene naphthalate), polyester diacetate, various glass materials, and microporous materials such as microvoided polyester described in copending U.S. Ser. No. 09/656,129, filed Aug. 29, 2000, polyethylene polymer-containing material sold by PPG Industries, Inc., Pittsburgh, Pa. under the trade name of Teslin(copyright), Tyvek(copyright) synthetic paper (DuPont Corp.), and OPPalyte(copyright) films (Mobil Chemical Co.) and other composite films listed in U.S. Pat. No. 5,244,861. The thickness of the support employed in the invention can be, for example, from about 12 to about 500 xcexcm, preferably from about 75 to about 300 xcexcm.
Antioxidants, antistatic agents, plasticizers and other known additives may be incorporated into the support, if desired. In a preferred embodiment, paper is employed.
In a preferred embodiment of the invention the porous ink-receptive layer contains inorganic particles such as silica, alumina, titanium dioxide, clay, calcium carbonate, barium sulfate, or zinc oxide. In another preferred embodiment, the porous ink-receptive layer comprises from about 10% to about 95% inorganic particles and from about 5% to about 90% polymeric binder, such as gelatin, poly(vinyl alcohol), poly(vinyl pyrrolidinone) or poly(vinyl acetate). The porous ink-receptive layer can also contain organic beads or polymeric micro-porous structures without inorganic filler particles as shown in U.S. Pat. Nos. 5,374,475 and 4,954,395, the disclosures of which are hereby incorporated by reference.
Examples of binders which may be used in the image-receiving layer include polyvinyl alcohol, polyvinyl pyrrolidone, poly(ethyl oxazoline), non-deionized or deionized Type IV bone gelatin, acid processed ossein gelatin or pig skin gelatin. The hydrophilic polymer may be present in an amount of from about 0.4 to about 30 g/m2, preferably from about 1 to about 16 g/m2.
The pH of the aqueous ink compositions of the invention may be adjusted by the addition of organic or inorganic acids or bases. Useful inks may have a preferred pH of from about 2 to 7, depending upon the type of dye being used. Typical inorganic acids include hydrochloric, phosphoric and sulfuric acids. Typical organic acids include methanesulfonic, acetic and lactic acids. Typical inorganic bases include alkali metal hydroxides and carbonates. Typical organic bases include ammonia, triethanolamine and tetramethylethylenediamine.
A humectant is employed in the ink jet composition of the invention to help prevent the ink from drying out or crusting in the orifices of the printhead. Examples of humectants which can be used include polyhydric alcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol and thioglycol; lower alkyl mono- or di-ethers derived from alkylene glycols, such as ethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol mono-methyl or mono-ethyl ether, propylene glycol mono-methyl or mono-ethyl ether, triethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, and diethylene glycol monobutylether; nitrogen-containing cyclic compounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-midazolidinone; and sulfur-containing compounds such as dimethyl sulfoxide and tetramethylene sulfone. A preferred humectant for the composition of the invention is diethylene glycol, glycerol, or diethylene glycol monobutylether.
Water-miscible organic solvents may also be added to the aqueous ink of the invention to help the ink penetrate the receiving substrate, especially when the substrate is a highly sized paper. Examples of such solvents include alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone, methyl ethyl ketone and diacetone alcohol; ethers, such as tetrahydrofuran and dioxane; and esters, such as, ethyl lactate, ethylene carbonate and propylene carbonate.
Surfactants may be added to adjust the surface tension of the ink to an appropriate level. The surfactants may be anionic, cationic, amphoteric or nonionic. A preferred surfactant for the ink composition of the present invention is Surfynol(copyright) 465 (Air Products) at a final concentration of 0.1% to 1.0%.
A biocide may be added to the composition of the invention to suppress the growth of micro-organisms such as molds, fungi, etc. in aqueous inks. A preferred biocide for the ink composition of the present invention is Proxel(copyright) GXL (Zeneca Specialties Co.) at a final concentration of 0.05-0.5 wt. %.
A typical ink composition of the invention may comprise, for example, the following substituents by weight: colorant (0.2-5%), water (20-95%), humectant (5-70%), water miscible co-solvents (2-20%), surfactant (0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).
Additional additives which may optionally be present in the ink jet ink composition of the invention include thickeners, conductivity enhancing agents, anti-kogation agents, drying agents, and defoamers.
The image-recording layer used in the process of the present invention can also contain various known additives, including matting agents such as titanium dioxide, zinc oxide, silica and polymeric beads such as crosslinked poly(methyl methacrylate) or polystyrene beads for the purposes of contributing to the non-blocking characteristics and to control the smudge resistance thereof; surfactants such as non-ionic, hydrocarbon or fluorocarbon surfactants or cationic surfactants, such as quaternary ammonium salts; fluorescent dyes; pH controllers; anti-foaming agents; lubricants; preservatives; viscosity modifiers; dye-fixing agents; waterproofing agents; dispersing agents; UV-absorbing agents; mildew-proofing agents; mordants; antistatic agents, anti-oxidants, optical brighteners, and the like. A hardener may also be added to the ink-receiving layer if desired.
In order to improve the adhesion of the image-recording layer to the support, the surface of the support may be subjected to a treatment such as a corona-discharge-treatment prior to applying the image-recording layer.
In addition, a subbing layer, such as a layer formed from a halogenated phenol or a partially hydrolyzed vinyl chloride-vinyl acetate copolymer can be applied to the surface of the support to increase adhesion of the image recording layer. If a subbing layer is used, it should have a thickness (i.e., a dry coat thickness) of less than about 2 xcexcm.
The image-recording layer may be present in any amount which is effective for the intended purpose. In general, good results are obtained when it is present in an amount of from about 2 to about 46 g/m2, preferably from about 6 to about 16 g/m2, which corresponds to a dry thickness of about 2 to about 42 xcexcm, preferably about 6 to about 15 xcexcm.